Don't pop the final controller in pager adapters. Fixes #681 (#682)

conductor-modules/viewpager/src/main/java/com/bluelinelabs/conductor/viewpager/RouterPagerAdapter.java

@@ -77,7 +77,8 @@ public abstract class RouterPagerAdapter extends PagerAdapter {
             savedPages.remove(position);
         }
 
-        Router router = host.getChildRouter(container, name);
+        Router router = host.getChildRouter(container, name)
+                .setPopRootControllerMode(Router.PopRootControllerMode.NEVER);
         if (!router.hasRootController()) {
             Bundle routerSavedState = savedPages.get(position);
 

conductor-modules/viewpager2/src/main/java/com/bluelinelabs/conductor/viewpager2/RouterStateAdapter.kt

@@ -155,6 +155,7 @@ abstract class RouterStateAdapter(private val host: Controller) :
   private fun attachRouter(holder: RouterViewHolder, position: Int) {
     val itemId = getItemId(position)
     val router = host.getChildRouter(holder.container, "$itemId", true, false)!!
+            .setPopRootControllerMode(Router.PopRootControllerMode.NEVER)
 
     // This should have already been handled by onViewRecycled, but it seems like this wasn't
     // always reliably called